The present invention relates to a method for forming a Chemical Vapor Deposition (CVD) film and an apparatus for manufacturing a semiconductor device with formation of an interlevel insulator in the semiconductor device.
There are a variety of CVD systems for forming an insulating film, but a plasma CVD method and a thermal CVD method have been principally used in recent years. However, an insulating film formed by the plasma CVD method is not suitable for a highly dense and fine pattern such as a very large scale integrated circuit (VLSI), in particular a dynamic random access memory (DRAM), since such insulating film has poor step coverage and contains impurities such as carbon (C).
Accordingly, attention has focused on application of the thermal CVD method because of its superior step coverage, in particular the thermal CVD method which enables film formation at such a low temperature that no thermal influence is exerted upon other components in forming a VLSI such as a DRAM.
Conventional methods include (a) a method involving oxidizing SiH.sub.4 or oxidizing SiH.sub.4 after mixing PH.sub.3 and B.sub.2 H.sub.4 therewith, and (b) a method involving pyrolyzing or oxidizing alkoxysilane Si(OR).sub.4 or oxidizing Si(OR).sub.4 after mixing B(OR).sub.3 and PO(OR).sub.3 therewith. Both (a) and (b) are conventional thermal CVD methods for forming a SiO.sub.2 film or an insulating film with a SiO.sub.2 film as the base.
Interlevel insulators are formed between Al and a gate and between Al and Al.
(1) For an interlevel isolator between Al and Al, the following are the criteria:
growth at a low temperature should be possible; PA1 the film should have low stress and low damage; PA1 the film should be highly dense and have controlled hillock of Al; PA1 the film should have stable electric characteristics; PA1 the film should have a flat characteristic; PA1 the film should have few pin-holes; PA1 the particle generation density should be low; and PA1 the film should have high durability. PA1 the film should be capable of reflow at a low temperature; PA1 the film should show stable electric characteristics; PA1 the film should have few pin-holes; and PA1 the particle generation density should be low. PA1 the cracking limit is increased, PA1 Al hillocks are not formed, PA1 self-flattening is increased, PA1 the density of the film is increased, and PA1 the stress is low, as compared with a conventional film of SiO.sub.2 only.
(2) For an interlevel insulator between Al and a gate, the following are the criteria:
Accordingly, a conventional plasma CVD method or atmospheric pressure CVD method may be used for forming an interlevel insulator between Al and Al, a complicated process wherein three types of a CVD film I 35, CVD film II 36 and a CVD film III 37 are formed on interconnection metals 34 on a substrate 33, as shown in FIG. 8. Optionally, a glass film may be applied midway therebetween for flattening and etch-back as shown in FIG. 9.
The following methods have been proposed for forming an interlevel insulator between Al and a gate:
(1) Formation of an arsenic silicate glass film using SiH.sub.4 -A.sub.S H.sub.3 -O.sub.2.
(2) Formation of a boron silicate glass film using SiH.sub.4 -B.sub.2 H.sub.6 -PH.sub.3 -O.sub.2.
(3) Formation of a boron arsenic silicate glass film using TEOS-Tri Methyl Borate (TMB)-Tri Methyl Phosphate (TMOP)-O.sub.3.
(4) Formation of a boron arsenic silicate glass film using TEOS-TMB-TMOP-O.sub.2.
(5) Formation of a germanium silicate glass film using SiH.sub.4 -GeH.sub.4 -PH.sub.3 -O.sub.2.
However, since reflow of the interlevel insulator can be performed at a temperature of approximately 800.degree. C. to 900.degree. C. in (1) to (5), it is possible to lower the reflow temperature, which, however, is not sufficient. In particular, the reflow temperature is lowered in (2) to (4) by adding arsenic or boron, but the film quality becomes unstable with the increase of the concentration of arsenic or boron.
Furthermore, according to the method for forming a germanium silicate glass film using SiH.sub.4 -GeH.sub.4 -PH.sub.3 -O.sub.2 in (5), there is the problem that the respective compounds are hydrides which are very active and very difficult to handle in practice and, thus, the method is unsuitable for mass production.
The present invention was created to address such various conventional problems, and has for its object provision of an improved method for forming a CVD film And apparatus for manufacturing a semiconductor device suitable for both formation of an interlevel insulator between Al and Al and formation of an interlevel insulator between Al and a gate and also suitable for mass production.